The invention relates to a process and an apparatus for cooling and purifying a hot gas containing slag particles.
Hot gas containing a sticky liquid and/or solid slag in finely-divided form is obtained when carbon-containing material, such as coal, brown coal, lignite, peat, petroleum coke, heavy residual petroleum fractions, and oil recovered from tar sand or bituminous shale, is completely or partly combusted. The gas is generated in an oven or reactor, and on leaving the oven or reactor generally has a temperature in the range of from 1300.degree. C. to 2000.degree. C. A suitable reactor for this purpose is described in the British patent specification No. 1,150,284.
The hot gas leaves the reactor at the top end, and then flows upwards through a substantially vertical pipe. A gas generated by partial oxidation consists for the greater part of H.sub.2 and CO, and possibly additionally of CO.sub.2, CH.sub.4, H.sub.2 O, N.sub.2, H.sub.2 S and Ar, and entrains sticky slag droplets and/or particles (dependent on the gas temperature and the nature of the inorganic components of the carbon-containing material to be combusted) from the reactor. In order to cool the hot gas rapidly to such a temperature that the sticky particles occurring therein lose their stickiness and the droplets solidify to non-sticky particles, a quantity of cold, clean gas is advantageously injected into the hot gas.
In conventional coal gasification plants, it has been usual to place a heat exchanger for cooling the generated gas above the gasification reactor. For relatively low capacities, this arrangement is practical, but for an apparatus in which a high rate of production of H.sub.2 - and CO-containing gas is possible, problems arise due to the great structural height involved. In an apparatus of this type, the reactor and the heat exchanger will, therefore, preferably be located next to each other.
A suitable apparatus and process are described in British patent application No. 8,209,664 now British Pat. No. 2,112,015. As described therein, the hot gas from the reactor flows upwards, is reversed to flow downwards, and is passed to the lower part of the heat exchanger. The slag particles are not yet separated from the hot gas mixture, but are further entrained by the gas mixture. The gas mixture is fed into a flow-deflection chamber located at the bottom of the heat exchanger. In the flow-deflection chamber, the velocity of the gas mixture is reduced. Due to the reduction of the velocity of the gas mixture and to the deflection, part of the slag particles settles and drops down to the bottom of the heat exchanger. Slag particles dropping down in the flow-deflection chamber must continuously or periodically be removed from the bottom. The slag particles, however, are still hot, which makes handling them troublesome. Moreover, valves and conduits used in the removal of the hot slag particles out of the bottom of the flow-deflection chamber are subjected to heavy erosion. The present invention provides a method for cooling and purifying a hot gas containing slag particles in which handling of the particles to be removed is relatively easy, and erosion of valves and conduits in the removal of slag particles is reduced to a great extent.